


Skirting the Line

by songlin



Category: Sherlock (TV)
Genre: Cunnilingus, Dressing Room Sex, F/M, Mirror Sex, Polyamory, Praise Kink, Semi-Public Sex, Vaginal Fingering, Vaginal Sex, Wedding Dress, fluffy dress as sex aid
Language: English
Status: Completed
Published: 2015-09-02
Updated: 2015-09-02
Packaged: 2018-04-18 17:29:50
Rating: Explicit
Warnings: No Archive Warnings Apply
Chapters: 1
Words: 2,575
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/4714388
Author URL: https://archiveofourown.org/users/songlin/pseuds/songlin
Summary: <blockquote class="userstuff">
              <p>Sherlock ducks under the hem and slips under the yards upon yards of gauzy white fabric. When Mary lets her skirts fall, he disappears. All she can see is a pair of men's shoes poking out from underneath and a vague, lumpy outline that could almost just be a fold in the dress.</p>
<p>That should not be nearly as hot as it is.</p>
            </blockquote>





	Skirting the Line

**Author's Note:**

> This was inspired by (and largely written at) this past Sherlock Seattle, when I saw a wedding dress in a window while discussing Marylock and got myself overexcited. I rediscovered it when going through all my Pages docs that I've written on my iPhone while lying in bed and that then just float around in iCloud until I remember them. Tweaked it some, added a couple hundred words or so, did a quick edit, and here we are.
> 
> This fic is tagged Johnlockary, though John is not directly present. Mary and Sherlock are fucking around inside of a polyamorous triangle, though, not behind John's back, and I wanted to make that clear. Still, I also figured I should forewarn anybody coming here for actual threeway sex.
> 
> [My visual for the dress was something close to this.](https://www.pinterest.com/pin/405886985139464391) Something that shared elements of the dress she ended up wearing, but generally WAY more over-the-top.

 

Mary looks at the picture she makes in the floor-length mirror opposite her.

"Oh, God," she says. "Definitely not."

"What?"

"It's very...very."

"What an illuminating description."

"Oh, come and have a look, then."

A hand pushes open the fitting room door. Sherlock steps inside and shuts it behind him.

Mary is standing on a slightly raised platform in front of a mirror. The shop attendant had explained that it allowed too-long dresses to fall naturally, to give an idea of what it would look like once hemmed. The dress Mary is wearing seems to fall for miles. The skirt is made of layers upon layers of gauzy tulle, tapering in towards the waist. The top is lace, lined and opaque over her waist and breasts, but sheer over the shoulders and down the sleeves. Mary looks over her shoulder to see the back and finds that the lace and lining plunge down nearly to her waist, and the transparent fabric exposes the bare skin of her back. A neat line of small buttons marches up her spine.

"I look like a cotton ball," Mary says.

Sherlock says nothing.

"Was I drunk when I came in here? I must have been. I maybe could have worn this when I was about…oh, twenty." She turns side to side, swishing the fluffy skirts. "God, Sherlock, find the attendant and—"

"Get this one."

Mary blinks. "I'm...sorry?"

Sherlock isn't looking at her face. He's looking at her from neck to toe to neck, over and over, slowly and with an inscrutable expression. His eyes move over 

"Get it." He takes a step closer, and Mary registers the dark flash in his eye just before his hands settle on her waist.

Mary snorts. "No."

"What?" Sherlock's expression shutters. Already on the defensive. Typical.

"We talked about this before we left. I walk in the dress, I pick the dress. And don't pout. Pouting won't change a thing."

Sherlock hastily scrubs his face clean of every trace of petulance. "I do not _pout."_

Mary smiles and thumbs his lower lip. "Pouting."

And oh, that look is back. She's playing a dangerous game, inviting that look out to play. The attendant could be back any second. They have no time at all really to pull this off, whatever "this" is.

Sherlock spans her waist with his hands. The raised platform she's standing on makes them roughly the same height. If anything, Mary may have an inch or so on him. It's quite the novelty, being able to get at this much of him. She could kiss his forehead, or eyebrows, or temples. She could get to the top of his head.

Instead, Mary takes him by the face, guides him in, and takes the opportunity to kiss him without getting a crick in her neck.

Sherlock is rubbing back and forth over her waist in small, predictable arcs. Then Mary tips her head back so their mouths break contact, and Sherlock's slides down to her neck and sideways to her collarbone.

"The attendant," she whispers.

"Is currently being dumped in the ladies' toilet," says Sherlock into her skin. Mary shivers. "I'd say we have at least...thirteen minutes?"

"She'll have to finish the phone call, and clean herself up so she's presentable," Mary agrees, rather breathlessly. "Might even ring a friend to talk it out."

"You know how girlfriends can be," Sherlock says. "Long-winded."

"Let's call it fifteen minutes," Mary says. "Help me back against the wall and fuck me. We're burning time."

Sherlock gathers the back of the skirt up in one hand and keeps the other on her waist. They walk backwards together, stepping off the raised platform and continuing, until Mary's back touches the full-length mirror against the far wall. Sherlock plants his hands on either side of her, leans in, and kisses her with luxurious care. Mary moans her approval. She tries to pull him in by the hips to measure his arousal, but she can't feel anything with all this damned fabric in the way. It doesn't seem to bother Sherlock. He lets out a little shuddering groan and cups the back of her head in his hands. Her hair will be hopelessly mussed. She'll come home and John will know exactly what they did and demand every last detail. He'll make Sherlock kiss him like this. They can never keep it tender for long, though, the two of them together. They take care with Mary, but with each other it's only a minute before someone's teeth catches someone's lip, or someone's nails dig into someone's flesh, and the ferocity between them catches light.

"Stop thinking about John," Sherlock growls.

"Kiss me like you kiss him and I might," Mary challenges in return.

Bless him, he does. His fingers in her hair wind tighter and tug, forcing her head back and giving Sherlock the space to drag his mouth down Mary's neck and latch on. She gasps.

"You'll leave a mark," she says. "The attendant…"

Sherlock glares reproachfully. "Make up your mind."

"I made up my mind five minutes ago, when you told me to buy the dress." She combs her fingers through his hair. "Now kneel down."

Without breaking eye contact, Sherlock slowly lowers himself to one knee. "Lift up your skirts," he says, in a voice like honeyed whiskey.

Mary gathers the front of the dress—it takes both hands—and raises them, little by little, up to her knees. Sherlock ducks under the hem and slips under the yards upon yards of gauzy white fabric. When Mary lets her skirts fall, he disappears. All she can see is a pair of men's shoes poking out from underneath and a vague, lumpy outline that could almost just be a fold in the dress.

That should not be nearly as hot as it is.

Two hands slide up her thighs, a breath of hot air puffs against her skin, and then Sherlock slips his fingers into the leg holes of Mary's knickers and tugs them down to her ankles. Mary exhales and keeps her breathing steady only by force of will.

From under her skirt, Sherlock says, "Put your leg over my shoulder."

Mary shakes her head, but of course Sherlock can't see that. "I'll tip over."

"Trust me."

"How many of John's near-death experiences start with that exact same sentence?"

Still, she leans back against the mirror, draws up her leg, and hooks it over Sherlock's shoulder. His hand comes up to caress the back of her knee, which makes her shiver.

"Sherlock," she says, letting the subtextual "get on with it" speak for itself.

He leans in and presses a wet kiss to the inside of her thigh.

"Getting there," Mary says. Her head is light and her face is warm.

She can feel Sherlock's skin on hers, the wisp of curl, the nudge of his nose, and finally, finally, his lips on hers, and a tongue swiping out to trace along her seam. Mary's toes curl. Sherlock's tongue is velvet-slick against her, sweeter than chocolate, and it leaves her craving. He doesn't deny her. Mary thinks fleetingly that they must be short on time—surely the attendant's been dumped by now—but then Sherlock stiffens his tongue and presses it up, it touches on her clit with a static shock of pleasure, and her thoughts fizzle out.

"Yes, that's it," she sighs. "Do that again."

So Sherlock does do it again, and again, and again. He eases pleasure out of her with exquisite care, using just a hair's breadth less pressure than what it would take to leave her gasping. So much for picking up the pace. Sherlock seems content to carry on like this all day.

Mary can't stop twitching under the onslaught. The leg slung over Sherlock's shoulder shifts, her foot rubbing back and forth over Sherlock's shirt. He moans, and the sound rumbles straight into Mary's clit. She gasps and arcs her back as if she can force herself harder onto Sherlock's mouth. She wants to grind down, to hump herself to orgasm, but Sherlock's head keeps moving. She can't get the proper pressure.

Then Sherlock's free hand traces up her leg, ankle to calf to knee to thigh and back, and there are two fingers teasing at her cunt. Mary claps her hand over her mouth to smother the gasp she knows will come as Sherlock circles once, then twice, then slides those two fingers up and in and hooks them with deadly precision. Mary's hips jerk, nearly knocking her off, but Sherlock's other hand wraps around her thigh like an iron band and steadies her. He strokes slowly but firmly, so hard Mary sees stars with every press. Suddenly, the pressure on her clit is exactly enough, and what she needs is friction. Just a little faster there, and steady there, and—God, how is she meant to speak when Sherlock can do _that?_

She manages to gasp out, "Faster," and Sherlock, bless him, obeys. He flicks her clit back and forth with his tongue, keeps stroking in and pressing, sucking, thrusting—

Mary's leg nearly kicks out as she comes. She tries to grab at Sherlock's shoulder to steady herself, but the skirt gets in the way, so she just slaps her hand to the mirror and bucks her way through.

She's only just gotten her head back when Sherlock shrugs her leg off, crawls out from under her skirts, and crowds her against the mirror, eyes are blazing. Mary watches him lick his lips and grins slyly.

"Turn around," Sherlock growls. "Hands flat on the mirror."

Mary's still a bit dazed from orgasm, but she recognizes a good idea when she sees one. She turns round and braces against the mirror. Behind her, Sherlock is dropping trou. Her body and skirts block her view, but it's nothing she's not seen before and will see again. He hoists up the back of the skirts and push them to her waist. Pillowed on her back, they're bulky enough to pile up to Sherlock's chest.

"You have _no idea_ what it's like." Sherlock cups Mary's bum, which she arches up to be more convenient for him. "What you look like."

Mary's eyes drift shut. "Tell me."

Sherlock's damp fingers trail over her cheek. Mary takes the hint and obligingly sucks them into her mouth, which makes Sherlock moan. _That's right, pretty boy, you're not the only one with skills._

"Your waist looks tiny," he says. "It looks as if I could just pick you up and—fuck."

Mary had scraped her teeth down the underside of Sherlock's fingers.

"And _this_ —" He splays one hand out over the sheer fabric over her back. "It's like you've been put behind glass. I can see, but I can never touch."

"Touch me now."

With one hand, Sherlock spreads her arse, exposing Mary's undercarriage. She can imagine what the other hand is doing, what it's holding.

"And those _skirts_. I nearly could have been under there with the attendant in the room, and she'd never have noticed." The blunt, hot head of Sherlock's cock nudges at Mary's cunt. She spreads her feet a little, bends more at the waist to give Sherlock more maneuvering room, and breathes very steadily.

"Think you should give your skills a bit more credit," Mary fires back, but her newfound clearheadedness is scattered to the wind when Sherlock thrusts in.

He doesn't take his time. His pace is punishing right off the bat, pounding in deep and hard and fast. Mary whimpers. She can't come again, not so soon. But every push inward ripples through her, aftershocks of deep pleasure rocking her back and forth.

"I can't," Sherlock gasps, "I—"

"Yeah," Mary says, "what are you waiting for? Nearly came in your pants under my dress, didn't you? Filthy boy."

Sherlock gasps. It's charming, how easy he is to fluster.

"You couldn't touch yourself that way. How desperate did that make you? Were you squirming for it? I felt your hand fidgeting on my leg. But you never did, you clever thing. You held me up, you gave me my pleasure, and you waited your turn. My wonderful, beautiful Sherlock."

Sherlock lets out a noise that sounds almost like pain. But judging by the way he's bent double and groaning with every thrust, Mary's on the right track. She keeps going.

"Were you hoping the attendant would come back in? Did you want to hear her ask what I thought about the dress? I could've answered her. 'I don't like the frilly bits up top, but I simply adore the way my husband's boyfriend can climb right up under there and eat me out without anybody seeing.'"

Sherlock whines through his teeth. Not long now.

"We could do this again at the wedding," she goes on, breathless but not about to stop. "John could fuck me in the cloakroom after the ceremony. Later, at the reception, before the speeches, you could crawl up under my dress and taste it, taste us both. And then you'd have to get up and give your speech, and the whole time you'd still taste us on your tongue."

Sherlock's mouth drops open and he throws his head back. He thrusts in hard, pelvis coming flush with Mary's arse, and he bites his lip to cut off a long groan as he comes, hips twitching with every pulse. Mary sighs with sympathetic pleasure.

After a moment, Sherlock goes still. Mary gives him that moment, then reaches back andpats his bum.

"Pants up. Get my purse. Don't drip come all down me."

Sherlock staggers back, trying not to make too much of a mess. He pulls up his pants and trousers and fetches Mary's purse from the chair. She accepts it with a peck on the cheek as thanks, rifles through it, and comes up with a menstrual pad. Sherlock hands her her knickers.

"Good boy," Mary says, just to be cheeky. Sherlock blushes. She applies the pad to her underwear and shimmies them up her legs. "That'll do me until we get home. You can stay sticky and miserable; you're not wearing a few thousand pounds in taffeta."

"Tulle," Sherlock says.

Mary sticks her tongue out at him. She straightens and gives herself the once-over in the mirror. The mark at her neck is nothing too obvious, and it doesn't look like there's anything on the gown itself. Sherlock's nothing if not neat.

Mary spots him watching her and trying to look like he isn't. She rolls her eyes.

"I'm still not getting the dress."

Sherlock is the picture of wounded pride. "What? Why not?"

"I told you, it's about two decades too young for me. My wedding, my pick. You can wear a lovely fluffy gown at your own wedding."

Sherlock looks so offended—so _outraged—_ at that that Mary can't not crack up. Sherlock sneers as if this is all impossibly beneath him.

There is a shy knock at the door. "Ms. Morstan? Doing alright?"

Mary fans herself with her hand to try to dry up the tears of laughter welling up. "Oh, yes," she calls back. "Nothing. Nothing at all." She straightens up, lifts her hem, and steps back up onto the little raised platform. "Could you find something with a little less...fluff?" She winks at Sherlock.  "I feel like I could fit two people in this."

 


End file.
